Method of casting



Oct. 31,- 1944.

E. L. A. CAMlN METHOD OF CASTING Filed Aug. 18, 1942 3mm ETIENNE LAIAMN Patented Oct-31, 1944 UNITED STATES PATENT OFFICE METHOD OF CASTING Etienne L. A. Camin, Wilmington, Del-., assignor to Louis Rosen, New York, N. Y.

Application August 18, 1942, Serial No. 455,163

9 Claims.

The present invention relates to casting, and

more particularly to a method and apparatus for casting objects of a relatively small cross section.

When molten metal is poured into a mold of restricted cross section, the resulting casting is of poor quality due to poor crystalline structure and to the existence of blow holes. Also oxida tion of the metal during the casting contributes to the poor quality of the casting.

According to the present invention the fore going factors contributing to poor castings are eliminated by heating a restricted portion of a mold by an induction heater, gradually feeding the metal to be cast into the mold and gradually raising the relative position of the heating means relatively with respect to the mold as the metal fed thereinto is fused.

An object of the present invention is to provide a method for casting fusible solids wherein the fusible solid is gradually fed into a mold, oxidation being prevented by keeping the heated metal in a neutral atmosphere.

Another object of the invention is to provide a method and apparatus for casting objects of small section and of high quality.

Still another object of the invention is to provide a method and apparatus of casting metalwherein the metal is fused in a mold having heat externally applied thereto.

A further object of the invention is to provide a method and apparatus for casting fusible solids wherein a mold is externally heated over a limited section, the section heated beginning at the bottom and gradually being raised to the top and the solid to be cast is gradually fed into the mold as the solid is fused.

These and other objects residing in the arrangement, combination and construction of the parts will be apparent from the following specification when taken with the accompanying drawing, in which Fig. 1 is a vertical section of a construction diagrammatically disclosing one form of the invention wherein apparatus for casting a rod is disclosed, and the metal to be cast is fed to the mold in the form of a wire,

Fig. 2 is a cross section of apparatus similar to that disclosed in Fig. 1, illustrating apparatus for casting a rod wherein the metal to be cast is fed to the mold in a granulated state, and

Fig. 3 is a cross-sectional figure of apparatus corresponding .to Fig. 1 disclosing the apparatus for casting a blade for a hollow airplane propeller wherein the metal fed to the mold is in the form of two wires.

Referring particularly to the drawing, the reference character I indicates a mold of a refractory material. The mold I is supported by a member 2, the member 2 being arranged to move the mold I vertically along its vertical axis. The mold I may be of any particular shape desired. In Fig. 1 it is elongated and cylindrical in form so that with the particular structure of Fig. 1 a casting in the form of a rod will be produced.

Disposed about a limted part of the mold I is a coil of tubing 3 constituting an induction heater. It will be understood that the terminal portions 4 of the induction heater 3 are connected to a conventional source of high frequency current in a manner well understood in the induction heating art. Metal to be cast is furnished in the form of a rod or wire 5 and is gradually fed into the mold through the top thereof. Disposed over the top of the mold I is a housing 6 for the purpose of subjecting the interior of the mold and the heated metal therein to a neutral atmosphere. The housing 6 is provided with an opening I for permitting the entrance of the rod 5 of the metal to be cast into the mold I. The housing Ii arranged to permit movement of the mold I under the action of the member 2.

In the operation of the embodiment of the invention disclosed in Fig. 1. the mold I is initially disposed in a position with respect to the induction heater 3 as disclosed in dotted outline, that is, in a position to have the bottom thereof within the influence of the induction heater 3. The mold I is filled with an inert atmosphere, which for many castable substances, including stainless steel with which the present invention has been successfully carried out, is hydrogen. However, it will be understood that any suitable inert atmosphere may be used so long as it is inert to the material being cast. The inert atmosphere is provided under a slight pressure through the housing 6. The slight pressure not only insures the maintenance of the inert atmosphere within the mold I, but also causes a portion of the same to be expelled through the opening I past the wire 5 thereby preventing the entrance of air through the opening I. The inert atmosphere employed should be subjected to whatever steps are necessary in order to insure that it is truly inert. For instance, hydrogen should be heated in the presence of copper to remove oxygen and passed, througha suitable desiccating agent or agents to remove moisture.

When the apparatus has been arranged as described and the induction heater 3 is in operation, the rod 5 of the metal to be cast is fed into the mold I. As the rod 5 is melted due to the heat generated by the induction heater 3, fused metal begins to build up in the bottom of the mold I. The mold is then gradually lowered with respect to the induction heater 3 to move the portion of the mold I containing fused metal out of the influence of the induction heater 3 and to move a new portion of themold I' into the influence of the induction heater 3. The timing of the movement of the mold I and of the feeding of the rod 5 should be such that the surface of the fused metal within the mold is always within the influence of the induction heater 3 and the rod 5 is moved into the influence of the induction heater 3 as fast as it is fused.

Asthe portion of the mold I containing the fused metal is moved from the influence of the induction heater 3, the metal solidifies within the mold I as shown by the crosshatched portion of the metal within the mold I in Fig. 1. As a result of the gradual melting of the metal to be cast and gradual solidifying thereof, the casting is provided withoutbubbles and free from turbulence. The neutral atmosphere prevents oxidation. Thus, there is provided a final casting of good physical and chemical structure. When the mold I is filled and the metal therein has solidified, the mold I is broken away from the casting.

Another embodiment of the invention is disclosed in Fig. 2 wherein a mold I is supported by a member II and has a limited part thereof surrounded by a coil of tubing constituting an induction heater I2, the terminals I3 of which are connected to a source of high frequency current. The member II is for the purposeof sup- 1 porting the mold and for moving the same vertically in the same manner as the member 2 of Fig. 1. Arranged at the top of the mold I0 is a housing I4 for-the-pur-pose of maintaining an inert atmosphere in the interior of the mold III in the same manner as-described with respect to the embodiment of the invention disclosed in Fig. 1. I

The difference between the embodiment of the invention disclosed in. Fig. 2 and that disclosed in Fig. 1 lies in the fact that instead of feeding the metal to be cast to the mold by a wire or rod, the metal to .be cast is fed in the form of granulations I5. 'I'hegranulations |5 are considered to represent any divided form in which the metal may be supplied to the mold I. The housing I4 is arranged in a manner corresponding to the arrangement of the housing 6 in Fig. 1

.for preventing the entrance of air into the mold I 0 during the feeding of the metal to be cast.

The operation of the embodiment disclosed in Fig. 2 is similar tothat disclosed in Fig. 1. The mold I0 is, at the beginning ofa casting opera-- tion, arranged so that the bottom'thereof is within the influence of the induction heater I2. As the metal to be cast is gradually fed to the mold and the metal to be cast is fused, the mold I0 is moved downwardly maintaining the surface of .the fused metal within the mold Ill withinthe influence of the induction heater I2, but at. the same time gradually withdrawing the portion of the mold having fused metal therein out of the influence of the induction heater I2. manner metal is gradually solidifying in one part of the mold III and fusing in another part of the mold l0 at the same time. When the mold III has been filled and the metal therein solidified the mold III is broken away from the casting.

Still another embodiment of the invention is disclosed in Fig. 3 wherein is illustrated the manner in which the invention may be employed for casting hollow or tubular bodies. In the embodiment-disclosed in Fig. 3, there is disclosed the casting of a hollow blade for an airplane propeller. The mold is provided with an external shell 2| and an internal shell 22. The shells 2| mold 20 is fused.

Disposed about a limited portion of the mold 20 is a coil constituting an induction heater 24, having the terminals thereof connected to a suitable source of high frequency current. Secured to the upper end of the mold 20 is a housing 26 corresponding to the housings 5 and I4 in the form of two rods or wires 21.

of Figs. 1 and 2 respectively for maintaining an inert atmosphere in the interior of the mold 20.

The metal to be cast is fed into the mold 20 The wires 21 should be thin and flexible enough to permit following the contour of the mold 20 as disclosed in the drawing. While one wire 21 could be used, two may be used for the purpose of expediting the feeding of the metal to the thin section be-. tween the shells 2| and 22. It will be understood that the housing 26 is arranged in a manner corresponding to the arrangement of the housing 6 in Fig. 1 to permit the passage of the wires 21 therethrough while at the same time preventing the entrance of air into the mold 20.

scribed.

In this When the mold 20 has been completely filled, and the casting therein solidified, the shells 2| and 22 are broken away, leaving a tubular member of the desired configuration as determined by the construction of the shells 2| and 22.

From the foregoing specification it, will be ap parent that the advantage of casting according to the present invention, instead of pouring surface may be obtained. Air or other holes are eliminated because of the lack of turbulence in casting. Therefractory from which the molds are constructed may be of any -suitable form which will stand the required temperature and still may be broken away. Quartz and quartz substitutes have proven highly satisfactory, since theygive a surface of high quality. In the description the molds have been shown as movable.

may be moved rather than the molds so long as the required relative movement between the two parts of the structure is obtained. The metal fed to the mold may not only be in the form of rods or wires but also may be in other elongated However, it 'will be understood that the induction heatersforms as strips or tubes. The induction heater coils are disclosed as being constructed of tubing to permit the circulation of cooling water. ever, solid coils could be used if no cooling water circulation is desired.

Having thus described my invention, what I desire to secure by Letters Patent and claim is:

1. A method of casting a fusible solid which comprises providing a mold with a closed bottom, heating a portion of the solid in the mold by induction to a temperature sufiicient tomelt the solid to be cast, and gradually feeding the solid to be cast into said mold as the level ofthe fused solid therein rises. 2. A method of casting a fusible solid which comprises providing a mold having a closed bottom, heating a portion of the solid in the mold by induction to a temperature sufilcient to melt the solid to be cast, and gradually feeding a strip of the solid to be cast into said mold as the level of the fused solid therein rises.

3. A method of casting a fusible solid which comprises providing a mold having a closed bottom, applying a high frequency current to a limited section of the mold commencing adjacent closed bottom to produce induction heating, gradually feeding an elongated piece of the solid to be cast into said mold as the level of the fused solid therein rises, relatively raising the level of the induction heating with respect to said mold, and controlling the rate of relative rising of said induction heating with respect to the rate of feeding the solid to result in a continuous melting of the solid, filling of the mold and solidifying of the solid in the portion of the mold from which the induction heating has moved.

4. The method of casting a fusible solid which comprises providing a mold having a closed bottom, heating a limited section of the mold by an induction heater at the closed bottom, gradually feeding the solid to be cast into said mold as the level of the fused solid therein rises, relatively raising the level of the induction heater with respect to said mold, and controlling the rate of relative raising of said heater with respect to the rate of feeding the solid to result in a continuous melting of the solid, filling the mold and the solidifying of the solid in the portion of the mold from which the heater has moved.

5. The method of casting a fusible solid which comprises providing a mold having a closed bottom, heating the mold substantially uniformly across its section and over a restricted portion of the mold including the closed bottom to a tem- Howperature suflicient to melt the solid to be cast, and gradually feeding the solid to be cast into said mold, relatively raising the level of the heated portion of the mold with respect to said mold, and controlling the relative raising of said heated portion with respect to the rate of feeding of the solid to result in a continuuos melting of the solid, filling 1p the mold and solidifying of the solid in the p )rtion of the mold formerly heated.

6. The method of casting a fusible solid which comprises providing a mold having a closed bottom, heating the mold substantially uniformly across its section and over a restricted portion of the mold including the closed bottom to a temperature sufiicient to melt the solid to be cast.

and gradually feeding an elongated piece of the solid to be cast itno same mold, relatively raising the level of the heated portion of the mold with respect to said mold, and controlling the relative raising of said heated portion with respect to the rate of feeding of -the solid to result in a continuous melting of the solid, filling up the mold and solidifying of the solid in the portion of the mold formerly heated.

7. The method of casting a fusible solid which comprises providing a mold having a closed bottom, heating the mold substantially uniformly across its section and over a restricted portion of the mold including the closed bottom to a temperature sufficient to melt the solid to be cast, and gradually feeding the solid to be cast into said mold, relatively raising the level of the heated portion of the mold with respect to said mold, and subjecting the heated solid during casting to a neutral atmosphere.

8. A method of casting a fusible solid which comprises providing a mold having a closed bottom, heating a limited section of the mold by an induction heater at the closed bottom, gradually feeding an elongated piece of thesolid to be cast into said mold as the level of the fused solid therein rises, relatively raising the level of the induction heater with respect to said mold, and subjecting the heated solid during casting to a neutral atmosphere.

9. A method of casting a fusible solid in a closed bottom mold comprising the steps of feeding the solid into the mold, heating a portion of the solid by induction as it is fed into the mold to melt the solid, and raising the area of heat application as the level of the solid rises to permit solidification of the casting solid upwardly from the bottom of the mold while melting is still taking place in the rising heating area.

ETIENNE L. A. CAMIN. 

